The pineapple (Ananas comosus (L.) Merr.) is one of the most popular tropical fruit in the world. World pineapple production was 18 million tons in 2009 (FAO, 2011). Beside fruits, pineapple fields yield large amounts of leaves that may be used for their high quality fibre or as feedstuff for ruminants (Ecocrop, 2011).

The pineapple is a stoloniferous herbaceous, short-lived perennial plant that can reach 0.75-1.25 m in height, with a short and thick stem and a very shallow root. The leaves are waxy, succulent, 50-180 cm long and sword-like, and bear sharp upcurved spines on the edges. The leaves are arranged in a rosette around the stem. Leaf colour is very variable: from uniform green to variously striped with red, yellow or ivory down the middle or near the margins. Offshoots emerge from the stem at leaf axils. They are divided into aerial suckers and basal suckers. Basal suckers allow ratooning, but ratoon crops yield less (see Forage management below) (Ecocrop, 2011). The flowers are small and trimerous, red or purple, borne on an inflorescence at the apex of the stem (Ecoport, 2010). Flowering occurs progressively from the base up to the apex of the stem. The fruits are berries that merge together and form a single, cone-shaped, juicy and fleshy fruit whose core is the former stem. The fruit develops in 20 days. The fruit is generally seedless and is very variable in shape, size, weight and colour (from greenish to reddish or yellowish). Flesh colour varies from nearly white to yellow (Morton, 1987).

Distribution

Pineapples are native to tropical America, but are now cultivated in many warm countries, between 25°S (sometimes down to 33°S) and N. They grow from sea level up to an altitude of 1800 m, though fruit size and quality are higher at low altitudes. It requires a high relative humidity. In subtropical regions it can only be grown in frost-free areas: frost and temperatures of 0-5°C can kill the crop in a few days (Ecocrop, 2011).

Forage management

Pineapple can be a useful agroforestry species (Ecocrop, 2011). Green material yield may range from 30 t/ha to 60-80 t/ha (Model et al., 2000; Göhl, 1982). The optimum yield is 60-80 t/ha for the first harvest. First ratoon crop yields approximately 10% less, the second ratoon crop 30% less (Göhl, 1982).

Environmental impact

Agroforestry systems

Pineapples are a valuable species for agroforestry systems and play a role in soil improvement in regenerative analog agroforestry systems (Hasan et al., 2008; Vaz, 2000). In Bangladesh, when grown together with jackfruit they can help to cover human vitamin requirements (Hasan et al., 2008).

Soil erosion control and shelter

The pineapple crop also offers protection against heavy rain and winds to intercropped species and to the soil (Uriza-Avila et al., 2005).

Nutritional aspects

Nutritional attributes

Pineapple plant forage is highly fibrous (NDF 58-73% DM) with a low crude protein content (4 to 7% DM). The dried leaves at the bottom of the stems have a lower nutritive value than green leaves (Kellems et al., 1979). Leaves should not be used for non-ruminants (Fuller, 2004).

Potential constraints

Spines

Pinapple leaves are spiny and contain bromelain (a proteolytic enzyme). They may injure and cause skin problems to the workers who cut the leaves to feed animals. Pineapple leaves should not be used to feed pigs and poultry (Göhl, 1982).

Pesticides residues

In Hawaii in 1982, heptachlor (a carcinogenic pesticide) was found in the milk from cows fed fresh chopped pineapple leaves. The pesticide had been used to control the ants that tend mealybugs (Morton, 1987).

Ruminants

Pineapple leaves are a medium-quality roughage for ruminants. It is possible to let cattle graze pineapple leaves but this practice tends to compact the soil and it is recommended to cut the leaves instead (Py et al., 1987). Pineapple leaves can be used fresh, artificially dried or ensiled. They must always be chopped before use. It is recommended to ensile pineapple leaves with molasses. Though the silage is relatively low in protein and high in fibre, ruminants can be daily fed 15-20 kg of fresh or ensiled plants when other feed is scarce. The dried leaves can be advantageously pelleted (Morton, 1987; Göhl, 1982).

In a long-term experiment covering several lactations, pineapple silage was fed as the sole roughage to dairy cows. After the second lactation, it caused lower milk yield, lower appetite, weight losses, lighter calf weights, coat abnormalities and pica. Milk production and abnormalities were corrected with a supplement of alfalfa hay. These problems were not considered to be specific to the pineapple silage but rather to the effect of prolonged silage feeding as the only form of roughage (Bishop et al., 1974).

Fattening and growing cattle

Pineapple leaves fed alone to fattening cattle resulted in higher intakes but lower daily weight gains and lower carcass characteristics resulting in reduced financial returns for farmers (Prachyalak et al., 2001). When pineapple leaves were mixed with fresh grass or offered with total mixed rations the results were different: the fattening cattle had increased intakes but also higher daily weight gain and better dressing characteristics, thus resulting in more profit (Prachyalak et al., 2001; Prachyalak et al., 1999). Good growth results (0.77 kg daily weight gain/animal) were obtained in steers fed on pineapple leaf silage supplemented with soybean meal as a source of protein, though this diet did not compare favourably with the control maize grain/alfalfa diet in terms of average daily gain and feed conversion (Kellems et al., 1979). The value of feeding both pineapple canning by-products and pineapple crop residues (leaves and stems) was demonstrated in the Philippines, where large scale feeding trials on cattle given pineapple pulp and pineapple leaf silage, together with a 35% protein concentrate at 0.6% body weight, gave daily live-weight gains of between 0.38 and 0.48 kg (Albarece, 1979 cited by Devendra, 1985).

Sheep

In sheep, an aqueous extract of pineapple leaves was found to have a moderate anthelmintic effect against gastrointestinal nematodiasis (Khalid et al., 2005).